Number Of Matings Research Articles

Chronically time-in or intermittently time-out? Differentiating time-out from a shortage of opportunities

Males that provide parental care may lose opportunities to acquire extrapair mates or secondary social mates. These opportunity costs can be estimated as the product of (1) the degree to which a male's participation in care makes him unready for mating (i.e. represents ‘time-out’ from the mating pool) and (2) the availability of potential mating partners. One stage of parenting may therefore be more costly than another because it depresses a male's probability of capitalizing on any given mating opportunity, and/or because it occurs when alternative mating opportunities are more abundant. To determine whether male parental care limits extrapair mating in house sparrows, Passer domesticus, we tracked changes in male extrapair mating success across stages of their nesting cycles. We then assessed whether periods of reduced extrapair mating by males coincided with a scarcity of fertilizable females, or whether certain activities placed males in time-out. We found that the number of potential extrapair mates was significantly higher on days when a male's social mate was fertile than during incubation or nestling provisioning; breeding synchrony consequently reduces the realized opportunity costs of male parenting. Nevertheless, males with nestlings to feed suffered greater opportunity costs than might be expected because of their relative inefficiency at obtaining extrapair matings with potentially available females. During the incubation stage, by contrast, the males' probability of extrapair mating per fertile female averaged four times higher. Thus, nestling provisioning apparently places males in a partial time-out, but male incubation does not. Males may be more fully engaged in the extrapair mating pool during incubation because they typically devote little time to this form of care and, when confronted with an increase in the abundance of extrapair mating prospects, they reduce the time they commit to incubation.

Access to multiple mates increases fecundity but does not affect per-offspring maternal investment in a marine gastropod

Females of many organisms mate more than once and with more than one male, suggesting that polyandry confers some advantage to the female or her offspring. However, variation in maternal investment in response to mate choice and mate number can confound efforts to determine if there are benefits of polyandry. Access to multiple mates could increase maternal investment in offspring via a number of different mechanisms. Few studies have determined if investment is influenced by mate choice and number, and data are particularly lacking for marine invertebrates. This study was designed to determine if maternal investment and offspring size increase with access to increasing numbers of mates in the protandrous intertidal slipper snail Crepidula cf. marginalis. Virgin female slipper limpets were exposed to one, three, or five potential mates and their fecundity, egg size, and hatchling size were measured for multiple clutches. Treatment had a significant effect on fecundity, with fecundity increasing with the number of potential mates. Treatment did not have an effect on the size of eggs or hatchlings, on the variation in egg size or hatchling size within broods, or on the frequency of oviposition. Treatment did alter the variation in average offspring size among females, but not in the way predicted by theory. The main result, that access to multiple mates does not have an effect on per offspring maternal investment, makes C. cf. marginalis an ideal candidate to study the effects of polyandry on offspring fitness without having to take into account confounding effects of variation in maternal investment.

Polyandry and postcopulatory sexual selection in a wild population.

When females mate multiply, postcopulatory sexual selection can occur via sperm competition and cryptic female choice. Although postcopulatory selection has the potential to be a major force in driving evolution, few studies have estimated its strength in natural populations. Likewise, although polyandry is widespread across taxa and is the focus of a growing body of research, estimates of natural female mating rates are still limited in number. Microsatellites can be used to estimate the number of mates represented in females' sperm stores and the number of sires contributing to their offspring, enabling comparisons both of polyandry and of two components of postcopulatory selection: the proportion of males that mate but fail to sire offspring, and the degree of paternity skew among the males that do sire offspring. Here, we estimate the number of mates and sires among wild females in the Hawaiian swordtail cricket Laupala cerasina. We compare these estimates to the actual mating rates and paternity shares we observed in a semi-natural population. Our results show that postcopulatory sexual selection operates strongly in this species: wild females mated with an average minimum of 3.6 males but used the sperm from only 58% of them. Furthermore, among the males that did sire offspring, paternity was significantly skewed. These patterns were similar to those observed in the field enclosure, where females mated with an average of 5.7 males and used the sperm from 62% of their mates, with paternity significantly skewed among the sires.

Indicators of recent mating success in the pipevine swallowtail butterfly (Battus philenor) and their relationship to male phenotype

A key determinant of the intensity of sexual selection acting on a trait is how variation in that trait is related to variance in reproductive success of individuals. This connection compels efforts to assess lifetime mating number and how it varies among individuals in a population. In the Lepidoptera, female mating success can be assessed relatively easily by counting by the number of spermatophores in the female’s copulatory sac but male mating success in the field can often only be documented by observing copulations. Here we report a method for identifying whether or not males have recently mated that relies on the effect of mating on the appearance of the male’s reproductive tract in the pipevine swallowtail, Battus philenor. In this species laboratory experiments reveal that during mating, components of a male’s reproductive tract become shorter, decrease in mass, and change in appearance, irrespective of male age. These changes persist for at least two days after mating. After documenting these indicators of recent mating, we examined the reproductive tract of 68 field-caught males and found that twelve (17.6%) showed strong evidence of having mated recently. We found that older males were more likely to have recently mated. In addition, the color of the dorsal hindwing, a feature that females use in mate choice, was significantly greener in males, that according to our criteria, had recently-mated than in males that had not.

Seven dimensions of personality pathology are under sexual selection in modern Spain

Personality variation is increasingly thought to have an adaptive function. This is less clear for personality disorders (PDs)—extreme variants of personality that cause harm in most aspects of life. However, the possibility that PDs may be maintained in the population because of their advantages for fitness has been not convincingly tested. In a sample of 959 outpatients, we examined whether, and how, sexual selection acts on the seven main dimensions of personality pathology, taking into account mating success, reproductive success, and the mediating role of status. We find that, to varying extents, all personality dimensions are under sexual selection. Far from being predominantly purifying, selective forces push traits in diverging, often pathological, directions. These pressures differ moderately between the sexes. Sexual selection largely acts in males through the acquisition of wealth, and through the duration (rather than the number) of mates. This gives a reproductive advantage to males high in persistence–compulsivity. Conversely, because of the decoupling between the number of mates and offspring, the promiscuous strategy of psychopaths is not so successful. Negative emotionality, the most clinically detrimental trait, is slightly deleterious in males but is positively selected in females, which can help to preserve variation. The general picture is that at least some PDs form part of high-risk alternative strategies, although a sole evolutionary mechanism is unlikely to apply to all traits. An evolutionary perspective on PDs can provide a better understanding of their nature and causes than we have achieved to date by considering them as illnesses.

The role of birth weight on litter size and mortality within 24 h of life in purebred dogs: What aspects are involved?

In humans, scientific evidence emphasizes the role of birth weight on neonatal welfare, morbidity and mortality. In canine species, defining normal ranges of birth weight is a harder issue due to a great morphological variability in size, body weight and breed.The aim of this study was to correlate birth weight with litter size and mortality within 24h of life in 789 pups from 140 litters of purebred dogs and to investigate the aspects that might affect these factors.Birth weight was influenced by maternal size, weight and age (P<0.001). The lightest pups were from toy sized or weighing up to 10kg bitches. Conversely, bitches aged 2–8 years whelped heavier pups than younger and older mothers. Birth weight was also related both to litter size, with heavier pups in smaller rather than in larger litters from medium sized bitches, and breed (P<0.05). Unexpectedly, birth weight did not differ between live born and stillborn pups. However, birth weight was lower in pups dying within 24h of life (P<0.05). High mortality of pups was related both to short pregnancies (P<0.05), also showing lighter litters (P<0.001), and to dystocic parturitions (P<0.001). Litter size was associated with parity, type and number of mating, and length of pregnancy (P<0.001).Low birth weight appears to predispose to early neonatal mortality suggesting a predominant role of the breed rather than size and weight in determining birth weight in pups.

A comparative approach to testing hypotheses for the evolution of sex-biased dispersal in bean beetles.

Understanding the selective forces that shape dispersal strategies is a fundamental goal of evolutionary ecology and is increasingly important in changing, human-altered environments. Sex-biased dispersal (SBD) is common in dioecious taxa, and understanding variation in the direction and magnitude of SBD across taxa has been a persistent challenge. We took a comparative, laboratory-based approach using 16 groups (species or strains) of bean beetles (genera Acanthoscelides, Callosobruchus, and Zabrotes, including 10 strains of one species) to test two predictions that emerge from dominant hypotheses for the evolution of SBD: (1) groups that suffer greater costs of inbreeding should exhibit greater SBD in favor of either sex (inbreeding avoidance hypothesis) and (2) groups with stronger local mate competition should exhibit greater male bias in dispersal (kin competition avoidance hypothesis). We used laboratory experiments to quantify SBD in crawling dispersal, the fitness effects of inbreeding, and the degree of polygyny (number of female mates per male), a proxy for local mate competition. While we found that both polygyny and male-biased dispersal were common across bean beetle groups, consistent with the kin competition avoidance hypothesis, quantitative relationships between trait values did not support the predictions. Across groups, there was no significant association between SBD and effects of inbreeding nor SBD and degree of polygyny, using either raw values or phylogenetically independent contrasts. We discuss possible limitations of our experimental approach for detecting the predicted relationships, as well as reasons why single-factor hypotheses may be too simplistic to explain the evolution of SBD.

Conception rates in farm mink (Neovison vison) in relation to first mating date, age and color variety.

The aim of the study was to analyze the effects of the first mating date, age and color variety on the conception rates in farm mink. We analyzed female mink reproductive performance in 492 Sapphire and 463 Standard Black females over 3 or 4 years. The analysis included the number of inefficient matings, the interval between the first inefficient mating and the efficient mating (copulation) and the conception rates. The results show a significant effect of female's age and color variety on the conception rates. The youngest, yearling females of either color needed a higher number of matings per conception, as compared to older, 2- and 3-year-old females. Black females demonstrated a higher number of inefficient matings (1.066), as compared with Sapphires (0.730). Yearling females were most often mated from 1 to 10 March, and older females from 11 to 20 March. Older females achieved better conception rates than the yearlings. Dates between 11 and 25 March proved to be the optimum for the first mating, since the highest conception rates were observed if the females had mated during this period.

Effects of Methyl Eugenol Feeding on Mating Compatibility of Asian Population of Bactrocera dorsalis (Diptera: Tephritidae) with African Population and with B. carambolae.

Males of some species included in the Bactrocera dorsalis complex are strongly attracted to methyl eugenol (ME) (1,2-dimethoxy-4-(2-propenyl) benzene), a natural compound occurring in a variety of plant species. ME feeding of males of the B. dorsalis complex is known to enhance their mating competitiveness. Within B. dorsalis, recent studies show that Asian and African populations of B. dorsalis are sexually compatible, while populations of B. dorsalis and Bactrocera carambolae are relatively incompatible. The objectives of this study were to examine whether ME feeding by males affects mating compatibility between Asian and African populations of B. dorsalis and ME feeding reduces male mating incompatibility between B. dorsalis (Asian population) and B. carambolae. The data confirmed that Asian and African populations of B. dorsalis are sexually compatible for mating and showed that ME feeding only increased the number of matings. Though ME feeding also increased the number of matings of B. dorsalis (Asian population) and B. carambolae males but the sexual incompatibility between both species was not reduced by treatment with ME. These results conform to the efforts resolving the biological species limits among B. dorsalis complex and have implications for fruit fly control programs in fields and horticultural trade.

A Generic Construction of Z-Periodic Complementary Sequence Sets with Flexible Flock Size and Zero Correlation Zone Length

Without limitation on the number of mates, Z-periodic complementary sequence (ZPCS) sets, which have potential applications in multi-carriers CDMA communication systems and MIMO channel estimation, can support more users than conventional complementary sequence sets. In this paper, a generic construction of ZPCS sets is proposed based on perfect sequences and orthogonal matrices. It generalizes the earlier constructions by Li et al., and produces new ZPCS sets which cannot generated by earlier ones. The parameters of our ZPCS sets are flexible and are thus suitable for different application scenarios.

Impact of individual movement and changing resource availability on male–female encounter rates in an herbivorous insect

Species often confront changing resource distributions that result from natural and anthropogenic processes. For species that reproduce on or in close association with particular resources (e.g. host plants), changing resource distributions could affect the success of mate finding. We examine how mate-finding behaviours in an herbivorous insect mediate the impact of changing host plant spatial distribution. We tracked movements of 84 Melissa blue butterflies (Lycaeides melissa) in the Great Basin of western North America. Track data revealed sex differences in movement: males spent more time moving fast and females more time moving slowly; males moved more ballistically and females moved more diffusely. These differences vary quantitatively, but not qualitatively, between environments with contrasting resource distributions.From these data we created and parameterised a computer model of male–female encounters and used it to examine implications of changes to the patchiness and abundance of host plants. We use the cumulative encounter time between each simulated male–female pair as a proxy for mating success, thus allowing for the consideration of different female behaviours. The simulations suggest observed movement parameters exist in a trade-off between individuals maximising the number of potential mates they encounter and the probability that each encounter leads to mating success. Increasing host plant abundance decreases encounter rates thus encouraging males to be more diffuse to compensate. Changing the local resource density, i.e. increasing host plant patchiness, accentuated these trade-offs: by decreasing cumulative encounter time in resource rich environments and increasing it in resource sparse ones. Thus we see that both spatial resource geometry at multiple scales and plasticity in male movement strategies are important factors to consider when seeking to understand population reproductive behaviour, for example when assessing ecological impact of development, determining range boundaries and slowing invasions or outbreaks.

Mating patterns of female Leon Springs pupfish Cyprinodon bovinus.

In a field study of Leon Springs pupfish Cyprinodon bovinus, two questions about female promiscuity were investigated. First, were females selective in the males with whom they spawned or were they unselective, spawning randomly among males? Second, how promiscuous were the females, i.e. with how many males did they spawn? If simply spawning with many males maximized a female's reproductive success, then females might be expected to spawn randomly with as many males as possible. Alternatively, if females were selective but engaged in multiple mating, they would limit their spawning to preferred males. In the only wild population of this endangered fish, breeding males defend closely associated territories in the shallow margins of a single desert pool. No territories were observed elsewhere in the pool. Therefore, all territorial males were present simultaneously and females could survey all of them, depositing any number of eggs with one, a few or many males. Rather than spawning randomly, females surveyed many males first, visited relatively few males and ultimately spawned with a small fraction of those available males. With increasing numbers of spawns, however, females increased the number of different mates with whom they spawned. Thus, females showed a bet-hedging tactic of having a narrow mate preference while also laying eggs in the territories of other males, possibly to reduce egg predation and to avoid inbreeding.

Old male sex: large ejaculate, many sperm, but few offspring

Reproduction induces non-trivial costs, such that both males and females should choose their mates carefully and invest their resources prudently. Male performance and thus their investment into ejaculates are often predicted to decrease with age and mating frequency, which may in turn negatively affect female fitness and thus feedback on the attractiveness of old males. Such reproductive senescence may be mediated by changes in the males’ oxidative status. Here, we investigated the effects of male mating frequency and age on male reproduction and oxidative status, and the respective consequences for female reproduction. We used the tropical butterfly Bicyclus anynana, in which counterintuitively older males have a higher mating success than younger ones. In once-mated males, spermatophore mass and sperm numbers strongly increased with age, while antioxidant defences and oxidative damage declined with age. In repeatedly mated males, spermatophore mass and sperm number showed little variation being similar to young once-mated males, while antioxidant defences increased and oxidative damage decreased with mating frequency. Female reproductive success was highest when mating with young once-mated males, although these produced small spermatophores with low sperm numbers. Our findings suggest that in B. anynana, (1) ejaculate size and sperm number are not reliable proxies of male quality, (2) ejaculate quality diminishes with age and mating number, and that (3) old male mating advantage likely results from sexual conflict owing negative effects on female fitness.

Enumeration of MOLS of small order

We report the results of a computer investigation of sets of mutually orthogonal latin squares (MOLS) of small order. For $n\le9$ we 1. Determine the number of orthogonal mates for each species of latin square of order $n$. 2. Calculate the proportion of latin squares of order $n$ that have an orthogonal mate, and the expected number of mates when a square is chosen uniformly at random. 3. Classify all sets of MOLS of order $n$ up to various different notions of equivalence. We also provide a triple of latin squares of order 10 that is the closest to being a set of MOLS so far found.

A New Adult Diet Formulation for Sterile Males of Anastrepha ludens and Anastrepha obliqua (Diptera: Tephritidae).

A new adult diet formulation was evaluated for sterile Anastrepha ludens (Loew) and Anastrepha obliqua (Macquart) males at the emergence and release facility of fruit flies in Mexico. The formulation consists of hydrolyzed protein, sugar, juvenile hormone analogue methoprene, and water. The proportion of the ingredients between the solute (4% hydrolyzed protein and 96% sugar) and solvent (10% methoprene and 90% water) was 5:1. This new formulation was called the 1:24 formulation. The main objectives of this study were to develop a simple way to supply the 1:24 formulation to adults and to compare the sexual performance of these flies with the performance of flies fed a standard diet (called the Mubarqui formulation) used at the emergence and release facility of fruit flies in Mexico. The preparation, time, and cost also were evaluated. The results showed no significant differences in the sexual behaviors of the males (number of males mating, number of males calling, mating latency, and mating duration) between the 1:24 formulation and the Mubarqui formulation. However, the cost and the required preparation time are much lower for the 1:24 formulation process than for the Mubarqui formulation process. Based on these results, we recommend the 1:24 formulation as an additional adult diet option in the handling of sterile flies. Its application is practical and does not require changes in packaging systems. The contribution of our findings and their potential application to the improvement of the sterile insect technique are discussed.

Public good provision in blended groups of partners and strangers

We experimentally analyze cooperation in blended groups, where some group members stay together (partners) and others are switching groups (strangers). Our results reveal that teams consisting partly of members with strangers display a lower productivity compared to teams of permanent group members only. First, strangers cooperate less than partners in blended groups. Second, individual effort decisions increase with the number of group mates who are of the same type. This second effect holds for both strangers and partners and is neither driven by beliefs nor conditional willingness to cooperate. We argue that social identity plays a role here depending on group composition and the individuals’ role in a group.

Polyandry and fitness in female horned flour beetles, Gnatocerus cornutus

Although polyandry is common, it is often unclear why females mate with multiple males, because although polyandry may provide females with direct or indirect fitness benefits, it can also be costly. Our understanding of polyandry is also restricted by the relative paucity of studies that disentangle the fitness effects of mating more than once with a single male and mating with multiple males. Here we investigated potential benefits and costs of polyandry in the horned beetle, Gnatocerus cornutus , while controlling for the number of matings. We found that female life span was independent of mating frequency, indicating that mating itself is not very costly. However, females that mated more than once laid more eggs and had greater lifetime reproductive success than singly mated females. Because the magnitude of these effects was similar in monandrous and polyandrous females, this improved fertility was due to multiple mating itself, rather than mating with multiple males. However, although polyandrous females produced more attractive sons, these males tended to have smaller mandibles and so may fare less well in male–male competition. These results indicate that polyandry is relatively cost free, at least in the laboratory, and has direct and indirect benefits to female fitness. However, because the attractive sons produced by polyandrous females may fight less well, the indirect benefits of polyandry will depend on the intensity of male–male competition and how free females are to exert mate choice. Where competition between males is intense, polyandry benefits via son attractiveness may be reduced and perhaps even carry costs to female fitness.

Influences on male reproductive success in long-lived Blanding’s Turtles (Emydoidea blandingii)

Knowing how the number and qualities of mates influence male reproductive success (RS) can help interpret mating-system dynamics that are important for conservation efforts. We combined parentage data (1999–2006) with data from a long-term life-history study (1953–2007) of Blanding’s Turtles (Emydoidea blandingii (Holbrook, 1838)) on the University of Michigan’s E.S. George Reserve to document the relative influence of mate number and quality on male RS. Blood samples were taken from &gt;92% of resident adults and tissue samples were taken from 723 hatchlings from 92 nests of 54 females over eight nesting seasons. The incidence of multiple paternity averaged 41.6% (N = 77), was variable among years (minimum–maximum = 15.4%–55.6%), and was positively associated with female age, body size, and clutch size. Repeat paternity was observed in 69.9% of sequential clutches of the same female separated by 1–7 years. Male RS was variable (1–40 offspring) and was positively associated with the number of mates and clutches sired. The youngest male to sire offspring was 22 years old. Adult movements that result in encountering different mates and (or) the ability to use attributes (e.g., size or age) to identify high-quality mates have the potential to substantially increase RS.

Bateman's principle is reversed in a cooperatively breeding bird

Bateman's principle is not only used to explain sex differences in mating behaviour, but also to determine which sex has the greater opportunity for sexual selection. It predicts that the relationship between the number of mates and the number of offspring produced should be stronger for males than for females. Yet, it is unclear whether Bateman's principle holds in cooperatively breeding systems where the strength of selection on traits used in intrasexual competition is high in both sexes. We tested Bateman's principle in the cooperatively breeding superb starling (Lamprotornis superbus), finding that only females showed a significant, positive Bateman gradient. We also found that the opportunity for selection was on average higher in females, but that its strength and direction oscillated through time. These data are consistent with the hypothesis that sexual selection underlies the female trait elaboration observed in superb starlings and other cooperative breeders. Even though the Bateman gradient was steeper for females than for males, the year-to-year oscillation in the strength and direction of the opportunity for selection likely explains why cooperative breeders do not exhibit sexual role reversal. Thus, Bateman's principle may not hold in cooperative breeders where both sexes appear to be under mutually strong sexual selection.

Testing the adaptive significance of sex-specific mating tactics in collared lizards (Crotaphytus collaris)

We tested whether territorial defence is adaptive in male collared lizards by examining the extent to which territory owners monopolize females. We also tested whether females benefit by mating with multiple males using alternative tactics when local sex ratios varied. Surprisingly, neither the number of offspring that males sired, nor the number of females that males mated with varied as a consequence of highly variable local sex ratios. Moreover, both the number of offspring sired and the number of female mates were independent of male social status. Courtship frequency was under positive directional sexual selection for mating success for territorial males. None of the phenotypic traits that we examined were targets of sexual selection in nonterritorial males. Although offspring survivorship decreased with the degree of multiple mating, females mated multiply with similar numbers of territorial and nonterritorial males during all three seasons. Females did not obtain material or genetic benefits that balanced the apparent offspring survival cost imposed by mating with multiple males. Instead, females appeared to be ‘making the best of a bad job’, perhaps because the abundance of hiding places used by subordinate males makes it difficult for females to avoid male harassment. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ••, ••‐••.